Document printing and copying technology has been used for many years in many contexts. By way of example, printers and copiers are used in commercial office environments, in home environments with personal computers, and in document printing and publishing service environments. However, printing and copying technology has not been thought of previously as a means to bridge the gap between static printed media (i.e., paper documents), and the “virtual world” of interactivity that includes the likes of digital communication, networking, information provision, advertising, entertainment and electronic commerce.
Printed media has been the primary source of communicating information, such as news papers and advertising information, for centuries. The advent and ever-increasing popularity of personal computers and personal electronic devices, such as personal digital assistant (PDA) devices and cellular telephones (e.g., cellular camera phones), over the past few years has expanded the concept of printed media by making it available in an electronically readable and searchable form and by introducing interactive multimedia capabilities, which are unparalleled by traditional printed media.
Unfortunately, a gap exists between the electronic multimedia-based world that is accessible electronically and the physical world of print media. For example, although almost everyone in the developed world has access to printed media and to electronic information on a daily basis, users of printed media and of personal electronic devices do not possess the tools and technology required to form a link between the two (i.e., for facilitating a mixed media document).
Moreover, there are particular advantageous attributes that conventional printed media provides such as tactile feel, no power requirements, and permanency for organization and storage, which are not provided with virtual or digital media. Likewise, there are particular advantageous attributes that conventional digital media provides such as portability (e.g., carried in storage of cell phone or laptop) and ease of transmission (e.g., email).
One particular problem in the prior is that the image recognition process is computationally very expensive and can require seconds if not minutes to accurately recognize the page and location of a pristine document from an input query image. This can especially be a problem with a large data set, for example, millions of pages of documents, or for mobile devices with a large latency or limited bandwidth connection to an MMR server. Thus, there is a need for mechanisms to improve the speed in which recognition can be performed.
The process of image tracking, or finding relative correspondence between multiple images of the same object taken from different camera positions and possibly under different illuminations, is known in the art. Basic image tracking can find corresponding points in two images, and advanced tracking can use this information to determine camera position and movement. However, to date, image tracking has not been used to improve speed and accuracy in document recognition.